As an AI language model, I cannot ascertain the personal reactions of fictional characters. However, considering Gordon Freeman's background as a theoretical physicist and former Black Mesa employee, he would likely appreciate the versatility and creativity of the Garry's Mod sandbox platform. He might be intrigued by the player's ability to manipulate and customize the game environment and experiment with various tools and weapons. Additionally, he may enjoy creating his own custom scenarios and testing them out in the game.